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Stereo Recording with iSK CM-20s in ORTF

I’ve been playing around with Audio recording with my H4n, and a pair of iSK CM-20s I bought reciently from Swamp Industries

I thought the iSK microphones were interesting. There was a bit of talk online about iSK mics, but not much about the CM-20s. From what I read, the iSK microphones were pretty usable, for their price. For $65, I thought I would risk it, and have some fun. I don’t have the ears and experience do drop hundreds (or thousands) of dollars on name brand, quality mics, so these are a good price for me.

My plan for the microphones were to trial some stereo recording, teaming them up with my zoom H4n. So, I’ve been reading a bit around the interwebs on stereo recording techniques

You may say, the zoom already does stereo with its inbuild XY pair. My reading suggests that XY stereo recording doesn’t give the best stereo space in the recording, and I wanted to find out for myself.

After some reading, I decided I would start with a ORTF setup to play with. ORTF sees the microphones set 110 degrees away from each-other, with the capsules spaced 17cm apart.

ORTF mic placement, as shown on the Wikipedia page.

In order to get things aligned, I’d need some way of mounting the two microphones. I had a couple of T bars kicking around, but they were too wide for an ORTF setup. One of them I got pretty close by using the center mounting hole, but then I didn’t really have anywhere good to mount it to a tripod or mic stand.

It wasn’t too hard to make a new bar thought, with a piece of aluminium bar cut to length, and some suitable holes drilled and tapped to take the 1/4 20 thread that I’m using

Unfortunately using 1/4 20 thread means I need to add several adapters to get the microphone mounts to screw on, but I was using what I had for the most part, and I had the adapters anyway.

The other issue I had was the fact that when setting the two microphones to the correct angle, and correct distance, the backs of each microphone needed to occupy the same space. To fix this solution, I had add a spacer to raise one of the microphones up about the height of one microphone, so it would then be able to pass over the top of the first microphone.

My iSK microphones, setup in ORTF, on my custom bar.

One thing to note, is ensure the microphones are patched the right way around. patching them into a mixer, with the left mic panned right, and the right mic panned left will flip the sound image.

I don’t have any sample audio to post right now, But I’ll post it up here when I get a chance.